Using the body to power batteries

Research focuses on eardrum, heartbeats, body heat to run devices
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Research demonstrating that energy produced in the inner ear could be used to power sensors is but one example of new study on using the body's own power sources to charge medical devices, according to a story published this week in the Wall Street Journal.

Researchers from the Massachusetts Institute of Technology and Harvard Medical School demonstrated in guinea pigs that they could power sensors for about five hours without inhibiting the animals' ability to hear.

Such low-power electronic devices might someday be used to monitor what's going on in the ears of people with hearing or balance impairments, or their response to therapies, such as for ear infections. In the future, they might also deliver therapies, according to a Harvard announcement.

Though this inner ear "battery"--from the vibration of the eardrum--has been known for 60 years, researchers had been stumped as to how use the 70 to 100 millivolts it produces. In comparison, an AA battery produces more than 10 times as much power, the Journal says.

Elsewhere, researchers are working to harness the power generated from heartbeats, blood flow, lung contractions and arm and leg movements, the story says.

The work increases the likelihood that patients with pacemakers, for instance, in the future would not have to undergo surgery to have the batteries replaced, as they do after five or 10 years. Some experts say that the first devices that use the body's energy could be on the market within a decade.

Challenging issues remain. Ensuring that the devices don't siphon off power that the body needs to function effectively remains a critical issue. The low wattage created intermittently means the power must be stored, though doing so could make devices too large to be implanted. Vendors' ability to make them ever smaller has been key to their proliferation.

At the University of Michigan, researchers are working to power a pacemaker from the heart's own beats. And using body heat to power a circuit is the focus of early research at Virginia Polytechnic Institute and State University.

In addition to harnessing internal power sources, new "smart" materials also hold promise to further advance healthcare. Researchers at the University of Illinois at Urbana-Champaign are working on biodegradable materials that can be used in implants that will do important work inside the body for a period of time, then dissolve away once that's done. They've also developed sutures that that detect and respond to signs of infection, helping wounds heal more quickly.

To learn more:
- read the Journal article
- here's the Harvard announcement

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